Dual-mode ISDN/STN video telephony terminal

Abstract

The disclosure concerns a dual-mode ISDN/STN visiophone terminal, including at least one audio equipment and one video equipment respectively connected to an ISDN via a dual-mode ISDN/STN audio coder/decoder incorporating an ISDN audio coder, an ISDN audio decoder, an STN audio coder and an STN audio decoder, and via a dual-mode ISDN/STN video coder/decoder incorporating an ISDN video coder, an ISDN video decoder, an STN video coder, and an STN video decoder, wherein in order to provide an answering/recording function in said visiophone terminal a RAM memory is used to store audiovisual messages in STN mode, and wherein the outputs of the ISDN audio and video decoders are connected respectively to the inputs of the STN audio and video coders in order to record in the RAM an audiovisual message sent by a calling party via a remote terminal, and wherein the outputs of the STN audio and video decoders are connected respectively to the inputs of the ISDN audio and video coders in order to send an audiovisual message, stored in the RAM, inviting said calling party to leave a message. The invention is applicable in the field of transmission and storage of audio and video data.

What is claimed is: 
     
       1. Dual-mode visiophone terminal for use on an integrated services digital network (ISDN) or a switched telephone network (STN), including at least one audio equipment and one video equipment respectively connected to an ISDN via a dual-mode ISDN/STN audio coder/decoder incorporating an ISDN audio coder, an ISDN audio decoder, an STN audio coder and an STN audio decoder, and via a dual-mode ISDN/STN video coder/decoder incorporating an ISDN video coder, an ISDN video decoder, an STN video coder, and an STN video decoder, wherein in order to provide an answering/recording function in said visiophone terminal a RAM memory is used to store audiovisual messages in STN mode, and wherein the outputs of the ISDN audio and video decoders are connected respectively to the inputs of the STN audio and video coders in order to record in the RAM an audiovisual message sent by a calling party via a remote terminal, and wherein the outputs of the STN audio and video decoders are connected respectively to the inputs of the ISDN audio and video coders in order to send an audiovisual message, stored in the RAM, inviting said calling party to leave a message. 
     
     
       2. Dual-mode ISDN/STN visiophone terminal according to claim 1, that also includes a dual-mode ISDN/STN multiplexer/demultiplexer, to multiplex the digital data of different types transiting the said terminal, that is connected to dual-mode ISDN/STN audio and video coders/decoders, to a physical interface between the said terminal and the ISDN, to a modem functioning in STN mode, and to means for setting up a visiophone call between said visiophone terminal and at least one remote calling terminal connected to the same ISDN. 
     
     
       3. Dual-mode ISDN/STN visiophone terminal according to claim 1, wherein said ISDN audio and video decoders constitute respectively a pre-analysis stage for said STN audio and video coders, enabling the quantity of information in the video signal to be reduced.